1. Field of the Invention
The present invention relates generally to a gas turbine engine, and more specifically to a seal between opposing slots that suffer from relative movement.
2. Description of the Related Art including information disclosed under 37 CFR 1.97 and 1.98
In a gas turbine engine, such as a large frame heavy-duty industrial gas turbine (IGT) engine, a hot gas stream generated in a combustor is passed through a turbine to produce mechanical work. The turbine includes one or more rows or stages of stator vanes and rotor blades that react with the hot gas stream in a progressively decreasing temperature. The efficiency of the turbine—and therefore the engine—can be increased by passing a higher temperature gas stream into the turbine. However, the turbine inlet temperature is limited to the material properties of the turbine, especially the first stage vanes and blades, and an amount of cooling capability for these first stage airfoils.
The first stage rotor blade and stator vanes are exposed to the highest gas stream temperatures, with the temperature gradually decreasing as the gas stream passes through the turbine stages. The first and second stage airfoils (blades and vanes) must be cooled by passing cooling air through internal cooling passages and discharging the cooling air through film cooling holes to provide a blanket layer of cooling air to protect the hot metal surface from the hot gas stream.
In order to increase the gas stream temperature, a spar and shell blade and vane design has been proposed. A spar and shell blade or vane includes a separate shell having an airfoil shape that is secured to a spar that functions as a support structure and a cooling air supply channel to the shell. Because the shell is a separate piece, it can be made from a different material such as a refractory material that has a higher melting temperature than the standard nickel super alloys currently used for cast blades and vanes.
In a gas turbine engine, the combustor and the turbine both have surfaces that must include a seal to prevent the hot gas from leaking through. These surfaces include combustor transition ducts, inter-segment gaps for blade outer air seals or duct segments, platform interfaces of turbine vanes, case-tied compressor stator vane segments, and seals between a spar and a shell in a spar and shell stator vane or rotor blade. Because these sealing surfaces are exposed to high temperatures, the opposing slots that receive the seal have a larger relative movement that results in the prior art seals to produce high leakages. The prior art seals are too rigid and not flexible enough in order to maintain a seal surface with the slots due to this high relative movement between the adjacent seal slots.